1. Field of the Invention
This invention relates to aqueous carbonaceous mixtures for transport by pipeline and more particularly to aqueous coal slurries stabilized with a condensation product of an aldehyde liberating composition, ketone and a sulfur dioxide liberating composition.
2. Description of the Prior Art
Transportation is one of the major problems involved in use of particulate carbonaceous materials such as coal. One transportation method uses aqueous mixtures such as water slurries. However, aqueous slurries of finely ground coal containing over 55 weight percent solids are difficult to move with slurry pumps. This is because as the solids level is increased above 50 weight percent, water and solids tend to separate causing coal particles to build up in various areas in the pumping system. Dewatering of the slurry causes blockage and jamming in the pumping system.
On the other hand, decreasing weight percent of water in aqueous coal slurries is desirable because water is a major contributor to the cost of transport and processing operations. The less water transported the greater the volume of coal that can be moved, resulting in transport efficiencies. Further, water resources are limited. Also, during burning of coal, a significant amount of heat is required to vaporize the water. As the weight percent of water decreases, efficiency of the coal burning process increases. Hence, use of higher weight percent solids aqueous carbonaceous slurries than was heretofore feasible would be of great importance.
It is known that anionic surfactants with sulfonate groups are dispersants for coal water slurries. Examples taken from the literature appear below.
U.S. Pat. No. 4,282,006 --Funk, Aug. 4, 1981, describes a pipeline pumpable coal water slurry having a high content of coal particles with a minimum of void spaces and a maximum of particle surface area to enhance dispersing effects generated by electrolytes and/or dispersing agents added to the slurry. For anionic dispersing agents, see column 29, line 53 to column 31, line 9.
U.S. Pat. No. 4,330,301 --Yamamura et al, May 18, 1982, describes anionic dispersants for aqueous coal slurries which are sulfonation products of polycyclic aromatic compounds, salts thereof and formaldehyde condensates thereof.
European Patent Application No. 0 078 938 --SKW Trostberg Aktiengesellschaft, publication date May 18, 1983, describes thermostable acid group containing condensation products of aldehydes and ketones which can be used in water systems as thickening agents, retention agents, surface active agents, dispersing or liquifying agents. Use of these condensation products in clay water suspensions and oil water coal suspensions is suggested.